应用科学：冬季奥运的幕后功臣－人造雪

人造雪已经成为冬季奥运中不可或缺的一部份。但是这种对人造雪的需求却可能会对环境造成损害。


在刚结束的2006年杜林冬季奥运会中，人造雪被广泛应用在许多的竞赛中，例如滑雪及滑雪板。事实上，今年杜林的雪下的比往常要薄，所以为了使比赛能够顺利进行，人造雪也可以说是必然的选择。而人造雪的好处除了制造足够的雪量之外，同时可以做出可以维持的较久而且状况较好的表面。对竞赛选手来说，人造雪可以使他们更容易创造新纪录。这种人造雪的技术在许多的滑雪圣地都已经被广泛的使用，以避免因为天气关系雪量不够而无法营业的情形发生。


制造人造雪主要是将水从一个喷嘴中高速喷出来然后利用高压空气将水滴吹到空中造成起雾般的效果，然后让这些液滴在空气中结成雪花。成功的关键是要让这些液滴在降落到地面之前就凝结起来。


现在因为地球环境暖化，所以找到好的滑雪场地已经越来越困难。举例来说，阿尔卑斯山的雪线已经逐年上升，对滑雪爱好者来说，的确不是个好消息。但是过度依赖人造雪也是会有问题。国际保护阿尔卑斯山组织(International
Commission for Protection of the Alps, CIPRA)的Michel Revaz就表示，制造人造雪要消耗水及能量。而这些人造雪所溶化的水也会对周围的生态系造成影响。


所以Revaz提了一个可能的折衷方案。他表示像冬季奥运这种大活动，不需要为了奥运就每四年建一堆造雪机器。把这些机器回收使用应该是个可以接受的方法。

Skiers take to man-made slopes

As demand grows for manufactured snow,
so does environmental impact.

by Helen Pearson

The 2006 winter Olympics is highlighting winter-sport enthusiasts' growing
reliance on man-made snow, and the toll that this addiction could take on the
environment.

All competitive ski and snowboarding events now take place largely on
man-made snow. Unlike its natural counterpart, the machine-made white stuff can
be carefully tweaked to make a more durable and consistent surface: one perfect
for record-breaking attempts.

The Olympic ski resorts outside Turin, Italy, have extensive snow-making
facilities and several new reservoirs were built for the games to supply water
for snowmakers. In recent weeks they have been piling on man-made snow, as the
natural stuff has proven rather thin on the ground in the Turin area this
season.

Snow-making equipment is viewed as essential in most ski areas to guarantee
coverage throughout the season. Nowadays, "natural snow is a bonus," says Rich
Brown of snow-making technology company York Snow in Victor, New York, whose
systems were used in the 2002 winter Olympics in Salt Lake City, Utah, and
previous games.

Nature's copycats

The art to snow-making is adjusting the water and air to ensure that the
water drops are small enough and sent far enough that they will freeze before
they hit the ground. If the air temperature is quite high, for example, dropping
the water content and upping the air would create smaller particles that are
more likely to freeze.

Snow-making machines also frequently incorporate nucleating agents in the
water: small quantities of materials such as bacterial protein, on to which the
water molecules attach and freeze. By triggering freezing, these agents raise
the temperature at which snow can be made.

Many resorts now use sophisticated computer systems that automatically adjust
the air and water output from snow machines based on air temperature, humidity
and wind, says Brown.

Skiing on ice

For race courses, experts adjust man-made snow to create a tough, fast and
icy course rather than a powdery one. A ski course is also heavily groomed and
often intentionally flooded to create patches of ice; these factors generally
determine the speed of a race.

There are other reasons for snow manufacturing to be in demand, beyond the
benefits of having a snow whose properties can be ordered up. Some predict that
the need for snow will rocket with the warming effects of climate change, which
are already pushing snow lines up the Alps.

But this comes with environmental costs, says Michel Revaz, of the
International Commission for Protection of the Alps (CIPRA), a conservation
group in Schaan, Liechtenstein. Making snow chews up energy and water, and can
rob rivers and creeks in the surrounding ecosystems.

One way to conserve the mountain environment, Revaz says, would be to reuse
winter sports competition facilities rather than building new ones. "It's not
clever to build a new piste every four years," he says. "It's time to say stop."